Extreme pressure lubricant



United States Fatent O Berkeley, Calif., assignors to Shell Development Company, Emeryville, Califl, a corporation of Delaware No Drawing. Application December 26, 1950, Serial No. 202,826

2 Claims. (Cl. 252-56) This invention relates to lubricants particularly suit- .able for lubrication under extreme operating conditions,

such as under extreme pressure, high speed and high temperature conditions.

It is well known that the high pressure occurring in certain types of gears and bearings may cause a film of lubricant to rupture with consequent damage to the machinery. It has been shown that base lubricants such as mineral oil and/ or synthetic oil can be improved with regard to their protective effect particularly on rubbing surfaces by the addition of certain substances, so that excessive wear, scuffing and seizure, which normally follow a breakin the film of lubricant, can be prevented even under the most unfavorable pressure and speed conditions. Lubricants possessing this highly desirable property are called extreme pressure lubricants.

It is known that certain elements or compounds of elements of the type of chlorine, sulfur, phosphorus and lead are capable of imparting extreme pressure properties to lubricants, which may be lubricating oils and greases, when blended therewith. Among the compounds heretofore used are notably the lead soaps, phosphoric acid esters, free or loosely bound sulfur, and certain chlorinated organic compounds. ,A principal objection to extreme pressure compounds of this class is that they are highly reactive with contacting surfaces causing etching, corrosion and discoloration of said surfaces.

Another objection to reactive extreme pressure agents is that they alter the original chemical nature of the contacting surface and this, under certain conditions, is undesirable. Additionally because of the activity of agents of the type under discussion they deplete rapidly resulting in, at the very best, only a temporary solution to extreme pressure lubrication.

It has now been discovered that improved extreme pressure lubricants can be obtained by introducing into a base lubricant a heat polymerizable polyfunctional organic compound containing a plurality of hydroxyl groups, including alcoholic and carboxylic hydroxyl groups, the oxygen content of the initial material not exceeding around about 2 /2 grams, per gram of carbon, said heat polymerizable compound being substantially unreactive with contacting metal surfaces being lubricated and substantially insoluble alone in the base lubricants to which it is added for imparting extreme pressure properties, thus forming a heterogeneous lubricating composition. In order to maintain the heat polymerizable compound .(suspensoid) in dispersion in the base lubricant, certain agents, which will be hereinafter fully identified, are admixed with the heterogeneous lubricant of this invention, the function of said agents being to suspend or maintain in the base fluid, as well as to activate, the extreme pressure properties of said heat polymerizable compound without making it reactive with contacting surfaces.

THE EXTREME PRESSURE AGENTS As broadly stated above, the extreme pressure agents of this invention are oil-insoluble heat polymerizable polyfunctional organic compounds containing a plural- 2,788,326 Patented Apr. 9, T957 ity of hydroxyl groups (or oxy groups such as keto groups capable of forming enols), preferably at least one carboxylic hydroxyl and one alcoholic hydroxyl radical (attached to carbon atoms) in the molecule, the oxygen content of the initial material not exceeding about 2 /2 grams per gram of carbon, said compounds being capable of forming highly viscous fusible polymolecular films between the rubbing surfaces. Representative and illustrative specific compounds which are embraced within the scope of this invention are tartaric acid, hydroxy malonic acid, citric acid, hydroxy glutaric acid, hydroxy adipic acid, malic acid, tartronic acid, oxalacet'ic acid, citraconic acid, mesaconic acid, aconitic acid, maleic acid, fumaric acid, itaconic acid, citraconic anhydride, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, sebacic acid, 'azelaic acid, 'suberic acid, laevulinic acid, pyruvic acid, acetoacetic acid, glyoxy'lic acid, hydroxy-butyric acid, glycollic acid, lactic acid, homoterephthalic acid or other polymerizable aromatic polyacids having a melting point below about 230 and mixtures of said acids. Any of these acids can be modified by esterification with a polyhydric alcohol to such a degree so as not to oil-solubilize said acids or interfere with the polymerization of the resulting oilinsoluble products under operating extreme pressure lubricating conditions so as to prevent formation of viscous fusible polymolecular film formation between contacting surfaces being lubricated. The polyhydric alcohols which are preferred are: ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and the like. Mixtures of the free acids and condensed esters of said acids can be used such as mixtures of tartaric acid and a condensed ester of tartaric acid with propylene glycol mixtures of citric acid and a condensed ester of citric acid with propylene glycol; mixture of lactic acid and an ester of tartaric acid with propylene glycol; mixtures of maleic acid and an ester of tartaric acid with ethylene glycol. Where mixtures of the free acid and condensable esters are used, it is preferred that the free acid be present in predominant amount, preferably from to of the mixture of the heat polymerizable compounds mentioned. Other compounds which can be used are carbohydrates such as sugars and derivatives thereof, :e. g. the pentoses and hexoses (ribose, arabinose, glucose, fructose, galactose, mannose, etc.)., amino-sugars, starch, degenerated cellulose, degenerated ethylcellulose; hexitols sorbitol, mannitol), glucarnine, salicylal glucamine and the like. The compounds can be pre-polymerized and then added to the base lubricant or the polymerization process can be, and preferably is, allowed to take place in situ, thus acting as a continuous supply of polymolecular film-forming materials between contacting metal surfaces, whereby preventing their wear.

SOLUBILIZING AGENTS The solubilizing agents for the extreme pressure additives of this invention are selected from oil-soluble materials which are less strongly adsorbed on metal surfaces than the extreme pressure agents and are preferably amphipathic non-ionic in nature, or mixtures of amphipathic non-ionic and ionic solubilizers can be used in which the non-ionic solubilizers are present 'in predominant proportion, preferably from 75% to 90% of the solubilizing mixture.

A. Non-ionic solubilizers The non-ionic solubilizers of this invention are alcohols, e. g. lauryl alcohol, oleyl alcohol, 4atertiary butyl .cyclohexanol, phosphatides, organic oxides, preferably the mono ethers .of polyalkylene glycol such as undecanoxy polyethoxy ethanol, esters, of which the oil-soluble partial respectively, on the other.

esters of polyhydric alcohols are preferred, said esters having at least one free hydroxyl radical. Tothis alcoholic portion of the molecule there is attached a predominantly hydrocarbon portion containing a number of carbon atoms, sufficient to give the molecule a'totalminimum carbon content of about :12 and preferably about 15 to 46 carbon atoms. This hydrocarbon portion is attached to the alcoholic portion of the molecule through an ester linkage which may be formed between the hydroxyl or an acid radical (if there is one), of the poly,- hydric alcohol on the one hand, and an acid or alcohol,

It is desirablethat the hydroxyl radicals and ester linkages of the'ester alcohol be as close together as possible, at least two hydroxyl radicals being separated from each other by not more than three directly connected atoms, and preferably being attached to vicinal carbon atoms. It is advantageous if the several polar groups are attached to directly connected carbon atoms. A

It will be seen that the ester alcohols may be derivatives of glycerine, erythritol, pentaerythritol, mannitol, s'orbitol, sorbitan, tartaric acid, etc. The acid (or alcohol, as the case may be) forming the ester with the polyhydric alcohol should have at least about 10, and preferably between about l and 40 carbon atoms, in the form of an aliphatic or cycloaliphatic radical.

Suitable radicals comprise, for example, capryl, decyl, undecyl, undecylenyl, lauryl, (dodecyl), tridecyl, myristyl (tetradecyl), myristolenyl, pentadecyl palmityl' (hexadecyl), palmitolenyl, oleyl, elaidyl, erucyl, stearyl, abietyl, etc. Radicals such as are contained in the acids obtained from resin or tall oil as well as naphthenic (i.e'. cycloaliphatic) acids having the requisite number ofcarbon atoms are also applicable.

The acid which may form the ester with the polyhydric alcohol is preferably a carboxylic acid, although sulfonic, alkyl sulfuric, phosphoric alkyl phosphoric, etc., acids are also useful. Specific monoesters are: glycerol monooleate, glycerol monostearate; sorbitan monooleate; sorbitan monostearate, glycerol monoricinoleate, glycerol mononaphthenate, mannitan monolaurate, mannitan monooleate, pentaerythritol monooleate, pentaerythritol monostearate, pentaerythritol monocaprylate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyethylene glycol monoand di-ricinoleate, glycerol monoester of soya bean fatty acids, etc.

B. Ionic solubilizers The use of ionic solubilizers in combination with the above non-ionic solubilizers is optional. Among the ionic solubilizers which are useful are the cation active and anion active compounds such as the nitrogen base compounds, e. g. amines, heterocyclic amines, e. g. glyoxalidine or imidazoline ring compound, e. g. l-hydroxy-ethyl- 2-heptadecenyl glyoxalidine, dimethylmono stearlamine, quaternary ammonium compounds; e. g. trimethyl benzyl ammonium chloride, sulfate, phosphate, dirnethyl distearly ammonium chloride and the like; soaps such as the amine and alkali metal, alkaline earth metal soap of fatty acids (Na, K or Ca oleate) or heavy metal soaps as well as oil-soluble sulfonates and sulfates or l-hydroxyethyl-Z hepta decenyl glyoxalidine soap of lactic acid. The weakly basic amines, being weakly-ionic surface aetlve agents, may serve in part the purpose of non-ionic agents. Therefore, they may be used to replace part of the strictly non-ionic agents. Preferred ionic-active agents are the glyoxalidines and soaps thereof or the oil-soluble organic sulfonates, obtained from petroleum sulfonic acids, such as the mahogany acids or oil-insoluble green acids produced in the manufacture of medicinal oils or refine- I ment of lubricating oils by treatment with fuming sulfuric .acid, oleum, chlorosulfonic acid, sulfur trioxide, etc.; or

the sulfo compounds may be derived from various aliphatic, alicyclic or aromatic compounds, such as alkylated benzenes, diphenyl, xylenes, diphenylmethanes, tetralines,

naphthalenes, anthracenes, phenanthrenes, alkyl phenolic compounds, alkylated halo aromatic compounds, e. g.

amines, diphenyl sulfides, phenyl naphthyl amines; alkylated pyridines, quinolines, isoquinolines, pyrroles, pyrrolidines, piperidine, thiophenes, thiophanes, etc.; or of various sulfonic acids of carboxylic. acid esters or amides; acids of the sulfuric: acid ester type such as turkey red oil, sulfated fish oils, sulfate acidsor mono ester of sulfuric acid obtained by treatment with strong sulfuric acid various olefines or alcohols such as the long chain olefines obtained in the vapor phase cracking of wax at about 550 C. polymers obtained by'polyme'rization of normally gaseous olefines with inorganic polyoxy acids or Friedel-Crafts catalysts; fatty ornaphthenic alcohols obtained in the catalytic reduction of fatty or naphthenic acids; alcohols obtained'by condensation of ketones or aldehydes followed by hydrogenation;- oralkyl aromatic mono esters of sulfuric acid, etc. Theabove compounds may contain substituent groups such as halogen, hydroxy, hydrosulfide, ether, amino, imino, sulfide, carboxyl, ester, etc. I

Any of the above-referred-to acids may be neutralized with alkali, alkaline earth metal basic compounds, ammonia, or organic nitrogen bases, to form salts thereof. Preferred are the sodium, potassium, calcium, barium, magnesium, ammonium andamine salts of the following specific sulfo acids: benzene sulfonic acid, toluene sulfonic acid, tri-isopropyl naphthalene sulfonic acid, polyamyl naphthalene sulfonic acid, diwax benzene sulfonic acid, oil-soluble petroleum sulfonic acid derived from various petroleum fractions, such as gas oil, kerosene, turbine oil, heavy oil, lubricating oil, petrolatum and mixtures thereof. In addition, sodium lauryl sulfate, sodium oleyl sulfate, ammonium lauryl sulfate and other alkali salts of'sulfated alcohols having from about 8 to 20 carbon atoms in the molecule may be used.

The salts of the sulfo acids may be replaced in part With salts of lauric, palmitic, stean'c, oleic, linoleic, ricinoleic acids, oxidized paraffin acids, tall. oil acids, rosin acids, abietic acid, wool fat acids, naphthenic acid, alkylated benzoic and naphthoic acids, aromatic fatty acids such as phenylacetic to phenylstearic acid, terpenic acid and the like. Also, the following salts can be used: Cu, Mg, Ca, Sr, Ba, Zn, Cd, Al, Sn, Pb, Cr, Mn, Fe, Ni, Co etc., and/or organic bases, e. g. fnitrogen .bases as primary, secondary and tertiary amines and quaternary ammonium bases of from 10 to 30 carbon thiophosphoric, arsonic and antimony acids; phosphonic and arsonic acids and the like.

Additional detergents are the alkaline earth phosphate diesters, including the thiophosphate, diesters; the alkaline earth diphenolates, specifically the calcium and barium salts of diphenol mono and poly sulfides.

BASE LUBRICANT.

Base oils to which agents of this invention are added may be selected from a variety of natural oils such 'as paraflinic, naphthenic, and mixed base mineral oils hav ing a viscosity rangesuch as from at F., SUS, to up to 250 SUS at 210 F. In addition, synthetic oils may be used such as polymerized olefins, alkylated. arm

matics; polyalkyl silicone polymers, e. g; liquid dirnethyl siliconepolymer, other silicone polymers, HzS-adducts of unsaturated ethers and thioethers, e. g. HzS adduct of dialkyl ether, di(2 ethyl hexyl) sebacate. Mixtures of natural and synthetic oils can be used. Under certain conditions of lubrication, minor amounts of a fixed oil such as castor oil, lard oil and the like, may be admixed with a hydrocarbon oil and/ or synthetic oil.

The general formulation of compositions of this invention can be represented by:

Amount (percent y w Broad Range Preferred Range Extreme Pressure Agent(s):

Oil-insoluble heat-polymerizable polyacidic organic compound e. g. tartaric acid, lactic acid, ester of propylene glycol-tartartic acid and mixtures thereof Solubilizer(s):

il-soluble non-ionic or mixture of nonionic with ionic solubilizers e. g. Sorbitan monooleate, polyoxyethylene sorbitan monooleate, sodium petroleum sulfonate,

etc Optional Additives:

Detergents, antioxidants, corrosion inhibir, etc

0.01 to 1D 0.001 to 5 Base.

Natural oil, e. g. mineral oil and/or fixed oils and derivatives thereof and/or synthetic lubricants Balance Preferred compositions of this invention are illustrated by the following examples:

Composition A Comments 1 Composition D Percent Tartaric acid 1.9 Gluconic acid 0.1 Sorbitan monooleate 4 Polyoxyethylene sorbitan monooleate 2 Mineral oil Balance Composition E Percent Tartaric acid 2 Glycerol monooleate a 4 Polyoxyethylene glycerol monooleate i 2 Mineral oil (SAE 90) a Balance Composition F Percent Condensed di-ester of tartaric acid and propylene glycol 2 Pentaerythritrol monooleate 4 Polyoxyethylene pentaerythritrol monooleate 2 Mineral oil (SAE 90) Balance Composition G Percent Succinic acid 1.33 Sorbitan monooleate 4 Polyoxyethylene Sorbitan monooleate 2 Ca petroleum sulfonate (oil soluble) 1 Mineral oil Balance Composition H Percent Condensed ester of tartaric acid and propylene glycol (15%) l-hydroxy-ethyl-2-heptadecenyl glyoxalidinc 0.02 Pentaerythritol monooleate 2 Mineral oil Balance Composition J Percent Mixture of condensed ester of ethylene glycol tartarate+10% glycerol 1-hydroxyethyl-2-heptadecenyl glyoxalidine lactate- 0.19 Pentaerythritol monooleate 2 Mineral oil Balance The following table illustrates additional compositions of this invention:

Composition l-hydroxy-ethyl 2-heptadecyl glyoxalidlne l-hyiroxy-ethyl 2-heptadecyl glyoxalldine lacta e Base:

Mineral lubricating oil Mineral lubricating oilalkyl naphthalene Polymerlzed olefin 1 The E. P. additives are present in amounts varying from 0.1 to 5%.

The solubilizers are present in amounts sufiicient to solubillze said E. P. agents and are present in amounts varying from two to four times that of the E. P. agent.

Speed: 3000 R. P. M. Test duration: mins. running at each load Specimen: involute spur gear (SAE 3312 steel) Compositions of this invention can be combined with other additives in lubricants, such as blooming agents, pour point depressants or viscosity improvers, antifoaming agents e. g. dimethyl silicone polymer and the like.

Antioxidants comprise several types, for example, alkyl phenols such as 2,4,6-trimethyl phenol, pentamethyl phenol, 2,4 dimethyl 6 -tertiary-butyl phenol, 2,4 dimethyl 6 octyl phenol, 2,6 ditertiary-butyl 4 methyl phenol, 2,4,6-tri-tertiary-butyl phenol and the like; amino phenols as benzyl amino phenols; amines such as dibutylphenylene diamine, diphenyl amine, phenyl-beta-naphthylamine, phenyl-alpha-naphthylamine, dinaphthyl amine.

Corrosion inhibitors or anti-rusting compounds may also be present, such as dicarboxylic acids of 16 and more carbon atoms; organic compounds containing acidic radical in close proximity to a nitrile, nitro or nitroso group (e. g. alpha cyano stearic acid).

Wear reducing agents which may be used comprise: esters of phosphorus acids such as triaryl, alkyl hydroxy aryl, or aralkyl phosphates, thiophosphates or phosphites and the like; neutral aromatic sulfur compounds of relatively high boiling temperatures such as diaryl sulfides, diaryl disulfides, alkyl aryl disulfides, e. g. diphenyl sulfide, diphen-ol sulfide, dicresol sulfide, dixylenol sulfide, methyl butyl diphenol sulfide, dibenzyl sulfide, corresponding diand tri-sulfides, and the like; sulfurized fatty oils or esters of fatty acids and monohydric alcohols, e. g. sperm oil, jojoba oil, etc.; in which the sulfur is strongly bonded; sulfurized long chain olefins such as may be obtained by dehydrogenation or cracking of wax; sulfurized phosphorized fatty oils or acids, phosphorus acid esters having sulfurized organic radicals, such as esters of phosphoric or phosphorus acids with sulfurized hydroxy fatty acids; chlorinated hydrocarbons, such as chlorinated paraflin aromatic hydrocarbons, terpenes, mineral lubricating oil, etc.; or chlorinated esters of fatty acids containing the chlorine in position other than alpha position.

Additional ingredients may comprise oil-soluble urea or thiourea derivatives, e. g. urethanes, allophanates, carbazides, carbazones, etc.; polyisobutylene polymers,

unsaturated polymerized esters of fatty acids and monohydric alcohols and other high molecular weight oil-soluble compounds.

Depending upon the additive used and conditions under which it is used, the amount of additive used may vary from 0.01 to 2% or higher.

It is to be understood that while the features of the invention have been described and illustrated in connec tion with certain specific examples, the invention, how,- ever, is not to be limited thereto or otherwise restricted, except by the prior art and the broad scope of the disclosed invention. a

The invention claimed is:

' 1'. A lubricating composition comprising a major amount of a mineral lubricating oil having incorporated therein from about a fraction of 1% to 10% of tartaric acid and from 2 to 20% of a mixture of sorbitan monooleate and polyoxyethylene sorbitan monooleate, each of said additives of said mixture being present in substantial amounts. 7 A

2. A lubricating composition consisting essentially of:

. Weight percent Tartaric a id Sorbitan mono l at 4 Polyoxyethylene sorbitan monooleate 2 Mineral oil Balance References Cited in the file of this patent UNITED STATES PATENTS 2,134,736 'Reuter Nov. 1, 1938 2,158,096 Werntz May 16, 1939 2,204,601 Kavanagh June 18, 1940 2,368,602 Weiss Jan. 30, 1945 2,370,299 Farrington Feb. 27, 1945 2,414,293 Farrington et al. .a Jan. 14, 1947 2,470,537 Waugh May 17, 1949 2,479,424 Sproule et al. Aug. 16, 1949 FOREIGN PATENTS 104,699 Australia Jan. 27, 1938 106,383 Australia Jan. 11,

OTHER REFERENCES Atlas Surface Active Agents; Atlas Powder Co., 1948, pp. 37, 38. 

1. A LUBRICATING COMPOSITION COMPRISING A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL HAVING INCORPORATED THEREIN FROM ABOUT A FRACTION OF 1% TO 10% OF TARTARIC ACID AND FROM 2 TO 20% OF A MIXTURE OF SORBITAN MONOOLEATE AND POLYOXYETHYLENE SORBITAN MONOLEATE, EACH OF SAID ADDITIVES OF SAID MIXTURES BEING PRESENT IN SUBSTANTIAL AMOUNTS. 